1. Field of the Invention
Embodiments of the present invention relate to an optical scanner changing the path of light. More particularly, embodiments of the present invention relate to a mirror package scanning apparatus having a simple structure and capable of two-dimensional scanning.
2. Description of the Related Art
An optical scanner is usually used to change the path of a laser, e.g., during the scanning of a two dimensional image. Such an optical scanner may further be easily used for a laser printer, a bar code reader, and the like. In addition, the optical scanner may perform more complicated operations such as complex image processing, e.g., for a laser television or the like. In such an environment, a laser may be provided along a certain path as a light source, so that a desired image may be obtained by two-dimensionally changing the path of the laser. A conventional method of using two mirrors, working with two respectively different axes, has been used so as to change the path of a laser. In addition, another method includes two-dimensionally changing the path of a laser by moving one mirror with two axes.
FIG. 1 illustrates a conventional optical system showing how the path of light can be changed by using two mirrors.
Referring to FIG. 1, the conventional scanner 10 includes a vertical projector 12 and a horizontal projector 14. Synthetic light may be modulated by image signals and reflected by the vertical projector 12, such that the path of synthetic light is changed in the up and down directions of a screen 16. The light reflected by the vertical projector 12 may again be reflected by the horizontal projector 14, so that the path of the light may be changed in the left and right directions of the screen 16. Here, the vertical projector 12 controls a rotation angle of a rotation shaft that is connected to a mirror, as a kind of Galvanometer, and changes the path of the modulated light in the up and down directions. To perform this horizontal scanning, the horizontal projector 14 rotates a polygon mirror and changes the path of the light in the left and right directions.
However, this scanner uses a general motor and occupies considerable space. Accordingly, it is difficult to manufacture such a scanner on a small scale. It is also difficult to reduce the noise and the vibration of the motor.
FIG. 2 illustrates another conventional method of changing the path of light using one mirror vibrating along two axes. This type of mirror may be manufactured by a MEMS process.
Referring to FIG. 2, the mirror 20 includes a reflector 22, a first torsion axis 23, an internal frame 24, a second torsion axis 25, and an external frame 26. The reflector 22 is coated to be reflective at the center of the mirror 20. The first torsion axis 23 is extended from the reflector 22 to opposite ends thereof. Here, the internal frame 24 is physically connected to the first torsion axis 23 and is provided around the reflector 22. The second torsion axis 25 is extended from the internal frame 24 and perpendicular to the first torsion axis 23. The external frame 26 is physically connected to the second torsion axis 25. First rotors are in the shape of a comb and provided on both ends of the reflector 22 at the center of the first torsion axis 23, with the first stators being in the shape of a comb and provided in the internal frame 24 in correspondence to the first rotors, and second rotors are in the shape of a comb and provided on both ends of the internal frame 24 at the center of the second torsion axis 25, with the second stators being in the shape of a comb and provided in the external frame 26 in correspondence to the second rotors.
As a high frequency of an alternating current is supplied to the reflector 22, the reflector 22 vibrates along the first torsion axis 23, i.e., in a seesaw manner. As a low frequency of another alternating current is supplied to the internal frame 24, the internal frame 24 may vibrate on the second torsion axis 25 at a relatively low frequency, compared to the vibration of the reflector 22. As a result, with such dual axial vibrations with a single mirror, image signals may be two-dimensionally distributed.
However, since the frequency of the reflector 22 is higher than the frequency of the internal frame 24, considering the characteristics of image signals, the electrodes for the reflector 22 and the internal frame 24 have to be insulated from each other and the shape of the electrodes may become very complicated. Electrodes are usually trenched, which may have a negative influence on the reliability of the structure. In addition, the reflector 22 and the internal frame 24 simultaneously vibrate on the second torsion axis 25. When this occurs, since the mass of the reflector 22 and the internal frame 24 is large, the reflector 22 and the internal frame 24 have to vibrate at relatively low frequencies, and it becomes very difficult to increase the frequency of the internal frame 24. In addition, a non-linearization of driving may occur and structural reliability problems may occur, due to dropping, impact and the like, for example.